Fiber reinforced plastic (FRP) is a modern material for light weighted constructions. However, by the inhomogenity of the material it is difficult to test it with conventional methods. This is valid as well for construction optimization as for nondestructive testing in production control. A good tool for the different tests is the holographic interferometry, because it invisions whole a field of deformations of a component under load. The use of holographic interferometry is shown in two examples which cover as well construction optimization as nondestructive testing: (1) Components of a radioastronomical antenna were investigated for construction optimization. The holographic interferometry was able to demonstrate the influence even of thin internal layers. (2) An application with different aspects is the test of an aircraft component. In order to detect defects, special loadings and special equipment has to be developed. The examples cover different aspects of testing fiber reinforced plastic components with holographic interferometry.